No central heating upstairs

[d000hg]

Ah, OK. So the manual override on the valve does bypass both the timer and the thermostat since the system is:

Honeywell -> Thermostat -> Valve -> Switch -> Boiler

Have I got that right or am I still missing something?

 

[stem]

Here's a simple sketch for you. The neutrals / earths are omitted for clarity, but it should help you understand what is happening. I have also assumed that you don't have a third valve supplying a hot water cylinder, but if you do, it follows the same pattern.



You may not have a separate programmer. If you have programmable thermostats that include both time and temperature control, then ignore the separate programmers.

 

[d000hg]

Many thanks No luck finding the valves so far but I'll look further.

 

[stem]

If they were installed when the house was built, they are generally together, usually in an upstairs cupboard, or airing cupboard if you have one.

 

[stem]

Ah, OK. So the manual override on the valve does bypass both the timer and the thermostat

The manual lever is there so that the valve can be fixed in an open position when the system is initially filled with water, to make sure the system is filled properly and to prevent airlocks forming. When manually open, it shouldn't operate the microswitch because you wouldn't want to have the system inadvertently running whilst filling it. I personally have never come across a two port valve that operates the microswitch when it is manually opened with the lever, because it doesn't normally travel far enough to do so. [Others have claimed to have had it happen though].